using ServiceStack.Text;

namespace ServiceStack.Script;

public static class ScriptPreprocessors
{
    public static string TransformCodeBlocks(string script)
    {
        var hadCodeBlocks = false;
        var processed = StringBuilderCache.Allocate();
        var inCodeBlock = false;
        var inMultiLineBlock = false;
        foreach (var line in script.ReadLines())
        {
            if (line == "```code")
            {
                hadCodeBlocks = true;
                inCodeBlock = true;
                continue;
            }
            if (inCodeBlock)
            {
                if (line == "```")
                {
                    inCodeBlock = false;
                    continue;
                }
                    
                var codeOnly = line.Trim();
                if (string.IsNullOrEmpty(codeOnly))
                    continue;

                if (codeOnly.StartsWith("{{"))
                {
                    inMultiLineBlock = !codeOnly.EndsWith("}}");
                    processed.AppendLine(codeOnly);
                    continue;
                }
                if (inMultiLineBlock)
                {
                    if (codeOnly.EndsWith("}}"))
                    {
                        inMultiLineBlock = false;
                    }
                    processed.AppendLine(codeOnly);
                    continue;
                }

                if (codeOnly.StartsWith("*") && !codeOnly.EndsWith("*"))
                {
                    processed.AppendLine(codeOnly.Substring(1));
                    continue;
                }

                processed
                    .Append("{{")
                    .Append(codeOnly)
                    .AppendLine("}}");
                continue;
            }
            processed.AppendLine(line);
        }

        if (inMultiLineBlock)
            throw new SyntaxErrorException("Unterminated '}}' multi-line block not found");
        if (inCodeBlock)
            throw new SyntaxErrorException("Unterminated '```code' block, line with '```' not found");

        if (hadCodeBlocks)
            return StringBuilderCache.ReturnAndFree(processed);
            
        // return original script if there were no code blocks
        StringBuilderCache.Free(processed);
        return script;
    }

    public static string TransformStatementBody(string body)
    {
        return TransformCodeBlocks("```code\n" + body + "\n```");
    }
}